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Acidity and basicity of thiocarboxamides in the gas phase
Author(s) -
Decouzon Michèle,
Exner Otto,
Gal Jeanfrançois,
Maria PierreCharles,
Waisser Karel
Publication year - 1994
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610070907
Subject(s) - chemistry , protonation , fourier transform ion cyclotron resonance , deprotonation , isodesmic reaction , molecule , decomposition , gas phase , ammonium , ion cyclotron resonance , ionic bonding , ion , inorganic chemistry , computational chemistry , organic chemistry , cyclotron
The gas‐phase acidity and basicity of thioacetamide and the basicity of N , N ‐dimethylthioformamide were measured by Fourier transform ion cyclotron resonance (FT‐ICR) mass sectrometry under conditions which minimized the extent of their decomposition. Thiocarboxamides are both much stronger acids and stronger bases than carboxamides. The relative stabilities of individual neutral and ionic species were assessed in terms of isodesmic reactions, using the published or estimated enthalpies of formation. The neutral molecules of carboxamides and thiocarboxamides are stabilized by interaction between the C = X and NH 2 functional groups. This interaction is of a similar magnitude in the corresponding protonated forms but it is of greater strength in the deprotonated forms. With regard to the difference between thiocarboxamides and carboxamides, the most significant factor is probably the Ione pair–Ione pair repulsion operating in the anions.